Rock Advice - Geology help.

[CrazedMichael]

How can i test for silicone if there is any present? Would boiling the sand remove it?

[CrazedMichael]

How much vinegar do i add to the water? I have added about a cup to tbe bucket and as of yet no fizzing. Maybe i need to add more? Like 50/50 vinegar/water?

[mrramsey]

I think you need to do 100% vinegar.

[Sebastian]

Hi Michael, I am a professional geologist. It is often notoriously difficult to judge rocks from pictures, especially if they are eroded. The first thing I do when someone gives me a rock is to take my hammer and smash it in half to take a look at an unweathered surface. But I don't think it is necessary to do that since you want to use them as ornaments. The first rock you showed I can't really tell from the picture, number two looks like an igneous rock of some sort (should be safe), and nr. 3 could be a typical layered sedimentary rock, or possibly a layered gneiss. Since all of them have been eroded in a river bed take this with a grain of salt. They should all be safe if they are negative for carbonates after you wash them thoroughly.

As others have pointed out it is good to use a mild acid to check if the rock has carbonates (e.g. calcite) in it. We usually use 10% HCl (hydrochlorid acid). you can often get a small portion at a phamacy. Vinegar might work, but it often bubbles less and can be hard to see. No need to submerge the whole rock, I have a small bottle with an eye dropper and 2-3 drops on the surface is all that is needed. Please note that rocks that do bubble are perfectly safe, they will just raise the PH. This might actually be a good thing if you have a rift lake tank.

Other than that I'd only be really cautious about rocks that look like and are often sold as lava rocks. Many igneous rocks contain heavy metal that can be harmful, but 'lava rocks' have a much more increased surface area to give off those toxic materials. They come from magma that outgassed near the surface and cooled down, trapping a lot of bubbles. Your rocks have a nice rounded surface and you don't have to worry about this.

In terms of the sand, there are usually two options. Either it is some sort of calcareous sand like you find it on some beaches in the tropics, or (much more likely) it is silica sand (SiO2). The former would react violently to any acid test because of the increased surface area. The latter is completely safe to use. That is what most sand consist off that you can buy as play sand, or aquarium sand. Don't worry about diatoms; while it is true that their skeleton is made out of silica, that does not mean you will suddenly have a diatom outbreak. If that was the case most fish tanks would look green. As a matter of fact, silica is extremely stable in most environments and should be the preference for any fish tanks if you don't want to change the water chemistry. Make sure the sand grains are reasonably round if you have fish that bury or look for food in the sediment.

[talldutchie]

Well, glad to have an expert on board.

Wanna take a stab at explaining this?

[CrazedMichael]

Wow, i was hoping to get a someone who has experience in using/testing rocks for aquariums that were not shop bought. But alas! we have a geologist on board!

Thanks for taking the time to explain and share your knowledge. So i can feel confident in using desert sand and those rocks in my tank and scape it to my liking.

The rocks have been soaking in the bucket with the vineger i ave added since my last post and havent done anything since. Tonight i play football again, so tomorrow night i will drain them and drip a few drops of vinegar on them. After that if they pass the test i will then boil them and leave to cool down naturally. This is just to make sure i havent picked up anything that may harm my fish such as parasites or any bugs.

At the end of next week i will look at collecting some desert sand and will boil that as well as someone suggested, again just to clean it really.

Then its time to rescape my 65g!


EDIT: Im not in any way worried about lava rock, because as far as im aware we have no volcanoes here in the UAE, or possibly in the Middle East for that matter.

[talldutchie]

There is nothing that will live in the baking sun out of water that will then survive a slightly acidic bath and then harm your fish.

[CrazedMichael]

Agreed - But i love my fish too much to not do everything i can to make sure they are clean

[CrazedMichael]

UPADATE:-

Rocks are finally in the tank. After the last post i had soaked them in vinegar for a week and at the end of the test no bubbles or foaming was present. So i emptied the bucket and gave the rocks a very good scrub in HOT water (hot enough that i can put my hands in) and dried them out. Left them out in the Dubai'an sun for 24hrs then washed again this time just in ordinary cold water. Put them back in a bucket with dechlorinated water and tested the PH and Hardness. Tested again last thursday and found no change.
Friday i drained the tank to 10% water left, took out the fish. Did a spring clean, trimmed and removed dead leaves. Rescaped the driftwood i had in there already and added the new rocks. Filled it back up and returned the fish. Here's how it stands now:-

FTS - New rocks on the right side and one i had already on the left.


Close up of the 2 larger ones, and of course, one of my discus.


Another shot of all 3 rocks. My Serpaes and Silvertips tend to bunch up more when i get too close with the camera!


Just for kicks.

[CrazedMichael]

Lastly, a FFTS.



Thanks to all those who provided some feedback and advise during this episode. Certainly enjoying my new scape and the extra colour the rocks bring.

I decided not to bother with the sand in the end. Might add that at a later date since i didnt want to put too much stress on the fish, discus in particular.

Stocking:-

2 x Angelfish
2X Discus
16 x Silvertip Tetras
11 x Serpae Tetras

I understand the tank is slightly over stocked, but i have 2 canisters rated at 200g each, and i do 50% WC/per week.